Hi Ivo,
These extensions are very similar, but they're different! The difference is Show Hide uses Javascript to show/hide meta boxes immediately when a condition changes (like selecting a page template, choosing post format, selecting category, etc.). That means the meta boxes always presents in the page, they're only shown/hid via Javascript. While the Include Exclude extension completely removes (excludes) the meta box from the page, no toggle effect when you change a condition, to see the meta box again you have to reload the page.
Both extensions are fast. Depends on what you need, you can choose one of them (or both).
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